CN110963964B - Continuous synthesis method of piroctone - Google Patents
Continuous synthesis method of piroctone Download PDFInfo
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- C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
- C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
- C07D213/89—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members with hetero atoms directly attached to the ring nitrogen atom
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Abstract
The application relates to a continuous synthesis method of piroctone, which comprises the following steps: providing a first solution and a second solution; and respectively and continuously pumping the first solution and the second solution into a microreactor, and reacting at 90-180 ℃ and 0.2-2 MPa to obtain piroctone. According to the synthesis method of piroctone, potassium tert-butoxide is used as a catalyst and alkali, isopropanol is used as a solvent, and a microreactor is used for realizing a continuous synthesis process, so that the yield of piroctone can reach more than 85%, the reaction time is shortened to be within 60 minutes, and the production period is shortened. In addition, the microreactor system has sealing property, so that contact reaction of hydroxylamine with oxygen, moisture and the like in the external environment is avoided, side reaction and loss of the hydroxylamine are greatly reduced, the post-treatment process is simpler, and the process is safer.
Description
Technical Field
The application relates to a micro-reaction synthesis method, in particular to a continuous synthesis method of piroctone.
Background
Piroctone, CAS number 50650-76-5, chinese alias 1-hydroxy-4-methyl-6- (2, 4-trimethylpentyl) -2 (1H) -pyridone, is a key material for the production of piroctone olamine. The piroctone olamine is an efficient, nontoxic and nonirritating antidandruff agent, can be well mixed with other additive components in shampoo, and is widely used in washing and caring cosmetics such as antidandruff shampoo, hair nourishing liquid, hair conditioner and the like.
The traditional synthesis method of piroctone takes 3, 5-trimethylhexanoic acid as a starting material, and is a four-step method for synthesizing piroctone, wherein one of key steps is to use 4-methyl-6- (2, 4-trimethylpentyl) -2-pyrone for hydroxylation reaction to synthesize piroctone. The hydroxylamine reaction is carried out by adding the starting materials into a 250ml single-neck flask in sequence: 4-methyl-6- (2, 4-trimethylpentyl) -2-pyrone, hydroxylamine hydrochloride and sodium methoxide. The optimized mole ratio of 4-methyl-6- (2, 4-trimethyl amyl) -2-pyrone, hydroxylamine hydrochloride and sodium methoxide is 1:2.8:2.8, the reaction temperature is 50 ℃, the reaction time is 15 hours, and the yield after salification is 73.2 percent.
The method adopts a kettle type intermittent synthesis process, so that the reaction time is longer, the product yield is lower, the materials are added in batches in sequence, the contact time of hydroxylamine hydrochloride solid and air is too long, and the hydroxylamine hydrochloride solid is easy to deliquesce or oxidate to lose efficacy, so that byproducts are generated, the post-treatment difficulty is increased, and the process safety is greatly reduced.
Disclosure of Invention
Based on this, it is necessary to provide a continuous synthesis method of piroctone, which can effectively shorten the reaction time, improve the product yield, and improve the process safety.
A continuous synthesis method of piroctone comprises the following steps:
providing a first solution comprising 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one, potassium tert-butoxide and isopropanol;
providing a second solution comprising hydroxylamine, water and isopropanol;
and respectively and continuously pumping the first solution and the second solution into a microreactor, and reacting at 90-180 ℃ and 0.2-2 MPa to obtain the piroctone ketone.
In one embodiment, the mass content of the 4-methyl-6- (2, 4-trimethyl amyl) -2H-pyran-2-ketone in the first solution is 10-30%, and the mass content of the potassium tert-butoxide is 5-20%; the mass content of hydroxylamine in the second solution is 10% -30%, and the mass content of water is 5% -20%.
In one embodiment, the molar ratio of the hydroxylamine to the 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one is (1-10): 1.
In one embodiment, the molar ratio of the hydroxylamine to the 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one is (2-6): 1.
In one embodiment, the molar ratio of potassium tert-butoxide to 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one is (1-4): 1.
In one embodiment, the molar ratio of potassium tert-butoxide to 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one is (2-3): 1.
In one embodiment, the temperature of the reaction is from 100℃to 150 ℃.
In one embodiment, the pressure of the reaction is between 0.5MPa and 1MPa.
In one embodiment, the residence time of the first solution and the second solution in the microreactor is from 0.2min to 60min.
In one embodiment, the residence time of the first solution and the second solution in the microreactor is from 0.5min to 30min.
According to the synthesis method of piroctone, potassium tert-butoxide is used as a catalyst and alkali, isopropanol is used as a solvent, and a microreactor is used for realizing a continuous synthesis process, so that the yield of piroctone can reach more than 85%, the reaction time is shortened to be within 60 minutes, and the production period is shortened.
In addition, the microreactor system has sealing property, so that contact reaction of hydroxylamine with oxygen, moisture and the like in the external environment is avoided, side reaction and loss of the hydroxylamine are greatly reduced, the post-treatment process is simpler, and the process is safer.
Drawings
Fig. 1 is a schematic diagram of a continuous synthesis scheme of piroctone in an embodiment.
Detailed Description
The present application will be described more fully hereinafter in order to facilitate an understanding of the present application, and preferred embodiments of the present application are set forth. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
An embodiment of the continuous synthesis method of piroctone comprises the following steps:
s110, providing a first solution comprising 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one, potassium tert-butoxide and isopropanol.
Wherein the mass content of 4-methyl-6- (2, 4-trimethyl amyl) -2H-pyran-2-ketone in the first solution is 10-30%, and the mass content of potassium tert-butoxide is 5-20%.
The 4-methyl-6- (2, 4-trimethyl amyl) -2H-pyran-2-ketone, potassium tert-butoxide and isopropanol are mixed to prepare a homogeneous liquid system so as to ensure the fluidity of the potassium tert-butoxide and the raw materials and improve the reaction and catalytic effects.
S120, providing a second solution comprising hydroxylamine, water and isopropanol.
Wherein, the mass content of hydroxylamine in the second solution is 10-30% and the mass content of water is 5-20%.
By mixing hydroxylamine, water and isopropanol, a homogeneous liquid system is prepared, so that the fluidity of raw materials is ensured, and a small amount of water has a synergistic catalytic effect.
It can be understood that by controlling the concentration of 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one, the concentration of potassium tert-butoxide in the first solution, the concentration of hydroxylamine and the concentration of water in the second solution, the viscosity of the reaction solution can be made smaller and easy to transport, and the reaction effect can be ensured to be better.
It should be noted that, step S110 and step S120 may be performed simultaneously or sequentially.
S130, respectively and continuously pumping the first solution and the second solution into a microreactor, and reacting at 90-180 ℃ and 0.2-2 MPa to obtain piroctone ketone.
In this embodiment, the molar ratio of hydroxylamine to 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one is (1-10): 1. Further, the molar ratio of hydroxylamine to 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one was (2-6): 1.
It should be noted that the molar ratio of hydroxylamine to 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one cannot be too large or too small, and too small may cause incomplete reaction, and too large may cause waste of hydroxylamine raw material and increase the post-treatment difficulty.
In this embodiment, the molar ratio of potassium tert-butoxide to 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one is (1-4): 1. Further, the molar ratio of potassium tert-butoxide to 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one was (2-3): 1.
The molar ratio of potassium tert-butoxide to 4-methyl-6- (2, 4-trimethyl amyl) -2H-pyran-2-ketone cannot be too large or too small, the too small catalyst effect of tert-butyl methanol is poor, the too large catalyst effect can cause side reaction, and the post-treatment difficulty is increased.
In this embodiment, the reaction in step S130 is carried out at 90℃to 180℃and further at 100℃to 150 ℃. By controlling the reaction temperature, the complete conversion of the raw materials can be ensured, and the product yield can be improved.
In the present embodiment, the reaction in step S130 is performed at 0.2MPa to 2MPa, and further, at 0.5MPa to 1MPa. The micro-reaction system is maintained in a liquid-liquid reaction system by controlling the reaction pressure, so that the water and the isopropanol are ensured not to be gasified at high temperature, the sufficient reaction residence time of materials in the micro-reactor is ensured, and the efficient mixing of the materials in the micro-reactor is ensured, so that the yield is further improved.
In this embodiment, the residence time of the first solution and the second solution in the microreactor is 0.2min to 60min, and further, the residence time of the first solution and the second solution in the microreactor is 0.5min to 30min.
It should be noted that, the residence time of the first solution and the second solution in the microreactor is determined according to the chemical reaction kinetics, and the flow chemical reaction kinetics equation is established by measuring and calculating the concentration of each reactant and each product under the residence time conditions of 90 ℃,100 ℃,110 ℃,120 ℃,130 ℃,140 ℃,150 ℃,160 ℃,170 ℃,180 ℃ in 0.05min,0.1min,0.2min,0.5min,1min,2min,5min,10min,20min,30min,45min,60 min. We have found that the higher the reaction temperature, the faster the reaction rate and the shorter the residence time required for the reaction. At 100 ℃, the retention time of 30min is 100 percent of the conversion rate of 4-methyl-6- (2, 4-trimethyl amyl) -2H-pyran-2-ketone; at 150℃the conversion of 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one was 100% with a residence time of 0.5 min.
In addition, the microreactor adopted in the application is a commercial universal microreactor, the hydraulic diameter of a microchannel is 0.1-30 mm, the total volume of the microchannel is 0.2-100 ml, the microreactor is made of stainless steel, hastelloy, silicon carbide ceramic and the like, and the microreactor has the advantages of good corrosion resistance, strong heat conduction and inertness to a reaction system.
The reaction formula of step S130 is as follows:
specifically, as shown in fig. 1, the advection pump 3 and the advection pump 4 respectively control the output of the first solution 1 and the second solution 2, so that the first solution and the second solution are pumped into the first solution inlet 6 and the second solution inlet 7 of the microreactor 5 at the same time according to a set flow rate, the first solution 1 and the second solution 2 are contacted in the microreactor 5 and initiate the hydroxylation reaction, the reaction temperature is controlled by the temperature control system 9, the reaction pressure is regulated and controlled by the back pressure valve 11, and the product flows out from the outlet 8 of the microreactor 5 and enters the product storage tank 10.
According to the synthesis method of piroctone, potassium tert-butoxide is used as a catalyst and alkali, isopropanol is used as a solvent, the raw materials and the catalyst form a homogeneous liquid system of a first solution and a second solution respectively, a continuous synthesis process is realized by adopting a microreactor, the catalytic effect is obvious, the yield of piroctone can reach more than 85%, the reaction time is shortened to be within 60 minutes, and the production period is shortened.
In addition, the microreactor system has sealing property, so that contact reaction of hydroxylamine with oxygen, moisture and the like in the external environment is avoided, side reaction and loss of the hydroxylamine are greatly reduced, the post-treatment process is simpler, and the process is safer.
The following are specific examples.
Example 1
The output of the first solution and the second solution was controlled using two advection pumps (model MPF0502C, shanghai three scientific instruments limited) such that the first solution and the second solution were simultaneously pumped into the first solution inlet and the second solution inlet of the microreactor, contacted and initiated the hydroxylation reaction within the microreactor.
Wherein, the micro-reactor:
model RMCS101010, manufactured by Shandong Haomai machinery Co., ltd
SiC material
Hydraulic diameter 1mm
Liquid holdup of the reaction pipeline: 17.2ml
The process conditions are as follows:
12wt.% of 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one, 12wt.% of potassium tert-butoxide, 66wt.% of isopropanol;
30wt.% hydroxylamine, 10wt.% water, 60wt.% isopropyl alcohol in the second solution;
the temperature of the microreactor is controlled to be 150 ℃;
the reaction pressure is 2Mpa;
hydroxylamine: 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one=3:1 (molar ratio);
potassium tert-butoxide: 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one=2:1 (molar ratio);
the reaction time in the microreactor is 0.5min;
analysis conditions:
c18 column (DIKMA Inertsil ODS-3column, 250X 4.6 mm)
Mobile phase: acetonitrile: water=80: 20 (v/v), flow rate 1.0ml/min
Detection wavelength 302nm
Area normalization quantification, sample amount 0.4. Mu.l
Retention time:
piroctone-7.04 min
4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one-9.82 min,
implementation results: piroctone yield 86.2%, other 13.8%, starting material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0.
Example 2 reaction temperature Change in microreactor
The reaction temperature in the microreactor was changed to 140℃in the same manner as in example 1, and the other experimental conditions and analysis methods were the same as in example 1. Implementation results: piroctone yield 85.1%, other 14.9%, starting material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0.
Example 3 reaction temperature Change in microreactor
The reaction temperature in the microreactor was changed to 130℃in the same manner as in example 1, and the other experimental conditions and analysis methods were the same as in example 1. Implementation results: piroctone yield 83.4%, other 15.8%, raw material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0.8%.
Example 4 reaction temperature Change in microreactor
The reaction temperature in the microreactor was changed to 160℃in the same manner as in example 1, and the other experimental conditions and analysis methods were the same as in example 1. Implementation results: piroctone yield 86.1%, other 14.9%, starting material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0.
Example 5 reaction temperature Change in microreactor
The reaction temperature in the microreactor was changed to 170℃in the same manner as in example 1, and the other experimental conditions and analysis methods were the same as in example 1. Implementation results: piroctone yield 85.7%, other 16.3%, raw material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0%.
Example 6 change in residence time of materials in microreactors
The residence time in the microreactor was changed to 1min in the same manner as in example 1, and the other experimental conditions and analysis methods were the same as in example 1. Implementation results: piroctone yield 86.0%, other 14.0%, starting material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0.
Example 7 change in residence time of materials in microreactors
The residence time in the microreactor was changed to 2 minutes in the same manner as in example 1, and the other experimental conditions and analysis method were the same as in example 1. Implementation results: piroctone yield 85.9%, other 14.1%, starting material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0.
Example 8 variation of the molar ratio of hydroxylamine to 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one
The molar ratio of hydroxylamine to 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one was changed to 2:1 in the same manner as in example 1, and the other experimental conditions and analysis method were the same as in example 1. Implementation results: piroctone yield 82.6%, other 17.1%, raw material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0.3%.
EXAMPLE 9 modification of the molar ratio of hydroxylamine to 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one
The molar ratio of hydroxylamine to 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one was changed to 4:1 in the same manner as in example 1, and the other experimental conditions and analysis method were the same as in example 1. Implementation results: piroctone yield 86.1%, other 13.9%, raw material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0%.
EXAMPLE 10 variation of the molar ratio of hydroxylamine to 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one
The molar ratio of hydroxylamine to 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one was changed to 10:1 in the same manner as in example 1, and the other experimental conditions and analysis method were the same as in example 1. Implementation results: piroctone yield 85.2%, other 14.8%, raw material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0%.
Example 11 reaction temperature and residence time in microreactor changes the reaction temperature in the microreactor was changed to 140℃and the residence time of the material was 1min in the same manner as in example 1, and other experimental conditions and analysis methods were the same as in example 1. Implementation results: piroctone yield 86.2%, other 14.8%, starting material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0.
Example 12 reaction temperature and residence time in microreactor the reaction temperature in the microreactor was changed to 130℃and the residence time of the material was 2min in the same manner as in example 1, and other experimental conditions and analysis methods were the same as in example 1. Implementation results: piroctone yield 86.2%, other 14.8%, starting material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0.
Example 13 reaction temperature and residence time in microreactor changes the reaction temperature in the microreactor was changed to 120℃and the residence time of the material was 5min in the same manner as in example 1, and other experimental conditions and analysis methods were the same as in example 1. Implementation results: piroctone yield 86.2%, other 14.8%, starting material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0.
Example 14 reaction temperature and residence time in microreactor the reaction temperature in the microreactor was changed to 100℃and the residence time of the material was 30min in the same manner as in example 1, and other experimental conditions and analysis methods were the same as in example 1. Implementation results: piroctone yield 86.2%, other 14.8%, starting material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0.
Example 15 reaction pressure Change in microreactor
The same procedure as in example 1 was followed except that the pressure in the microreactor was changed to 1MPa and the other experimental conditions and analysis methods were the same as in example 1. Implementation results: piroctone yield 86.2%, other 14.8%, starting material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0.
Example 16 reaction pressure Change in microreactor
The same procedure was followed as in example 1 except that the pressure in the microreactor was changed to 0.5MPa and the other experimental conditions and analysis methods were the same as in example 1. Implementation results: piroctone yield 78.2%, other 12.3%, raw material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 9.5%.
EXAMPLE 17 modification of the solution formulation of 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one
The ratio of the solution of 4-methyl-6- (2, 4-trimethyl amyl) -2H-pyran-2-ketone is changed into: 10wt.% of 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one, 20wt.% of potassium tert-butoxide, 70wt.% of isopropanol. Calculating to obtain potassium tert-butoxide: 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one=4:1 (molar ratio), other experimental conditions and analytical methods were the same as in example 1. Implementation results: piroctone yield 85.8%, other 15.2%, starting material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0.
Example 18, 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one solution ratio Change
The ratio of the solution of 4-methyl-6- (2, 4-trimethyl amyl) -2H-pyran-2-ketone is changed into: 20wt.% of 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one, 10wt.% of potassium tert-butoxide, 70wt.% of isopropanol. Calculating to obtain potassium tert-butoxide: 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one=1:1 (molar ratio), and the other experimental conditions and analysis method were the same as in example 1. Implementation results: piroctone yield 84.9%, other 15.0%, raw material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 0.1%.
Comparative example 1: sodium methoxide is used to replace potassium tert-butoxide
The ratio of the solution of 4-methyl-6- (2, 4-trimethyl amyl) -2H-pyran-2-ketone is changed into: 12wt.% of 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one, 5.8wt.% of sodium methoxide, 82.2wt.% of isopropanol. Calculating to obtain sodium methoxide: 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one=2:1 (molar ratio), and the other experimental conditions and analysis method were the same as in example 1. Implementation results: piroctone yield 76.9%, other 13.0%, raw material 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one 10.1%.
As can be seen from example 1 and comparative example 1, the yield was increased from 76.9% to 86.2% using potassium tert-butoxide instead of sodium methoxide.
The foregoing examples illustrate only a few embodiments of the application and are described in detail herein without thereby limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.
Claims (4)
1. The continuous synthesis method of piroctone is characterized by comprising the following steps:
providing a first solution comprising 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one, potassium tert-butoxide and isopropanol;
providing a second solution comprising hydroxylamine, water and isopropanol;
continuously pumping the first solution and the second solution into a microreactor respectively, and reacting at 90-180 ℃ and 0.2-2 MPa to obtain piroctone;
wherein the mass content of 4-methyl-6- (2, 4-trimethyl amyl) -2H-pyran-2-ketone in the first solution is 10-30%, and the mass content of potassium tert-butoxide is 5-20%; the mass content of hydroxylamine in the second solution is 10-30%, and the mass content of water is 5-20%;
the molar ratio of the hydroxylamine to the 4-methyl-6- (2, 4-trimethyl amyl) -2H-pyran-2-ketone is (1-10): 1;
the molar ratio of the potassium tert-butoxide to the 4-methyl-6- (2, 4-trimethylpentyl) -2H-pyran-2-one is (2-3): 1;
the residence time of the first solution and the second solution in the micro-reactor is 0.2 min-60 min.
2. The continuous synthesis method of piroctone according to claim 1, wherein the reaction temperature is 100 ℃ to 150 ℃.
3. The continuous synthesis method of piroctone according to claim 1, wherein the pressure of the reaction is 0.5MPa to 1MPa.
4. The continuous synthesis method of piroctone according to claim 1, wherein,
the residence time of the first solution and the second solution in the micro-reactor is 0.5 min-30 min.
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| EP0710650A2 (en) * | 1994-11-02 | 1996-05-08 | Hoechst Aktiengesellschaft | Process for the preparation of 1-hydroxy-2-pyridones |
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| CN103360308A (en) * | 2012-03-28 | 2013-10-23 | 孙伟新 | 1,4-dyhydroxy-6-methyl-2-pyridine ketone compound, and preparation method and use thereof |
| CN105541851A (en) * | 2015-12-16 | 2016-05-04 | 南京工业大学 | Synthesis method of 1, 2, 3, 4-tetrahydroquinoline derivatives |
| CN107474003A (en) * | 2017-09-29 | 2017-12-15 | 中国科学院大连化学物理研究所 | A kind of method of continuous synthesis N methyl pyrrolidones and N ethyl pyrrolidones |
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2019
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0710650A2 (en) * | 1994-11-02 | 1996-05-08 | Hoechst Aktiengesellschaft | Process for the preparation of 1-hydroxy-2-pyridones |
| CN103360308A (en) * | 2012-03-28 | 2013-10-23 | 孙伟新 | 1,4-dyhydroxy-6-methyl-2-pyridine ketone compound, and preparation method and use thereof |
| CN103242228A (en) * | 2013-04-27 | 2013-08-14 | 南京工业大学 | Method for continuously and controllably preparing small-size pyrithione granules |
| CN105541851A (en) * | 2015-12-16 | 2016-05-04 | 南京工业大学 | Synthesis method of 1, 2, 3, 4-tetrahydroquinoline derivatives |
| CN107474003A (en) * | 2017-09-29 | 2017-12-15 | 中国科学院大连化学物理研究所 | A kind of method of continuous synthesis N methyl pyrrolidones and N ethyl pyrrolidones |
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